Simple single-slit sound diffraction

"A stereo speaker is located inside a speaker cabinet with an opening 30.9 cm wide. The speaker emits a sound with a frequency of 2620 Hz. Assuming that the speed of sound in air is 343 m/s, find the location along a wall 97.7 m away where a listener will hear the first diffraction minimum. Give this location as a distance from the central axis. "

2. Relevant equations

I believe the relevant equation for this is the equation for the diffraction of waves through a single slit: